mm-Wave Waveguide Traveling-Wave Power Combiner Design Using an Equivalent Circuit Model

The waveguide traveling-wave power combiner (WTWPC) falls into the category of asymmetrical non-isolated power combiners, and, therefore, the active load modulation occurring within the combiner was investigated. Proper manipulation of active load modulation gave rise to a two-step design method for the combiner. The first step formulated the specifications of the combiner in terms of active load impedance at its input ports, which determined the objective scattering parameters of the combiner, as well as the desired coherent excitation signals. The second step established a versatile equivalent circuit model to provide a mapping relation between the scattering parameters and the physical dimensions of the combiner. The proposed equivalent circuit method not only offered a close-to-reality description of the existing type of traveling-wave power combiners but also broke new ground for combiner variants that accommodate the more general driving amplifiers. A Q-band quasi-planar traveling-wave waveguide spatial combined amplifier was built to demonstrate the proposed method. The measured P-JdB bandwidth of the prototype was 6 GHz (33-39 GHz).